Because both are absolute perfection.
Since its founding in 1992, Pagani has produced just two models: the Zonda and Huayra. That may sound like nothing when compared to Ferrari and Lamborghini. Obviously the latter two have been around for decades longer, but in its extremely short history, Pagani has managed to alter (in its favor) the very definition of a supercar. Take the Zonda, for example. It debuted in 1999 but was on the market for a decade, thus allowing Pagani to perfect it through many updates and special editions.
Then, in 2011, the Huayra was unveiled. Car porn was taken to an entirely new level. Both cars are powered by AMG-built V12s. Production takes place at Pagani's Modena factory, where a small and skilled team of craftsman create these masterpieces. So is there really any comparison between them? Is one better than the other in any way? Or is it simply a matter of personal taste? We'd gladly own either one. Beggars can't be choosers, after all.